Question: $ { {4} \times \left[\begin{array}{r}{2} \\ {4} \\ {1}\end{array}\right] = {?} } $
Explanation: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{r}{4}\times{2} \\ {4}\times{4} \\ {4}\times{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{8} \\ {16} \\ {4}\end{array}\right]}$